The invention relates to an anti-skid device for motor vehicles with a plurality of chain strands retained by a support which can be set into a revolving motion and connected to the latter by intermediate pieces forming resilient spreading arms, of which the ends remote from the support are thrown away from the support by the effect of centrifugal force when the support revolves in the service position, and at least parts of which pass through the region of the ground contact surface of the tyre when the vehicle tyre rotates.
An anti-skid chain of the above-mentioned type, in which each intermediate piece is adjoined by an individual chain strand made of links of comparatively great nominal thickness, is known from German Offenlegungsschrift No. 2,914,366. Its advantage compared to customary anti-skid chains lies in the fact that it renders time-wasting chain assembly superfluous. The driver of a vehicle, particularly a commercial vehicle, can on the contrary transfer the anti-skid device from a rest position into a service position and vice versa without leaving the driving seat. The fact that the known anti-skid devices of similar construction have also found little adoption in practice is due particularly to the fact that their anti-skid characteristics are unsatisfactory. Thus, particularly at low vehicle speeds, there is no guarantee that anti-skid elements will pass in sufficient number to the region of the ground contact surface of the tyre. The tyre--one may say--"does not accept the chain strands". There is the further factor that the rolling comfort of the tyre is greatly impaired when the known device is used, and despite the use of resilient spreading arms its chain strands tend to so-called braiding, which proves to be extraordinarily critical here because the spreading arms consist of a core formed by a cable piece or a chain strand section and a resilient rubber envelope enclosing the latter, through which the connection of the spreading arms to the support is effected. In the case of braiding, but also in the case of normal service, the forces acting in the region of the connection points can in fact assume values which cannot be withstood by the rubber envelope anchorage.
A similarly constructed anti-skid device is also known from U.S. Pat. No. 3,068,949, wherein instead of chain strands, resilient spoke-like structures are used which are connected by metallic tension springs to the support. Although this device presents the advantage that its anti-skid elements are moved into the region of the ground contact surface of the tyre irrespectively of the centrifugal force exerted upon them, and the danger of braiding is eliminated with them, nevertheless its anti-skid characteristics are unsatisfactory. Furthermore, the resilient construction of the spokes themselves and their connection by a traction spring to the support triggers a whiplash effect when the spokes are released after passing over the tyre, which can lead to damage not only to consecutive spokes but also to parts of the vehicle.
Anti-skid devices with anti-skid elements formed by rigid or resilient spokes have moreover failed to find acceptance for the additional reason that it is quite impossible, or at best only possible by accepting a substantial structural outlay, to accommodate them compactly in the out-of-service position.